Process for hydrogenating sulphur compounds



Pussies May 26, 1936 v a 2,041,840 M UNITED STATES PATENT \OFFICE-PROCESS FOR HYDROGENATING SULPHUR COMPOUNDS Wilbur Arthur Lazier,Marshallton, Del., and

John Victor Vaughen, Lakewood, Ohio, assignors to E. I. du Pont deNemours & Company, Wilmington, Del., a corporation of Delaware NoDrawing. Application August 3, 1934,

- Serial No. 738,206

9 Claims. (01. 260-16) This invention relates to the use of chromium Thefollowing examples are illustrative of the oxide in catalytic reactionsand more particularinvention, but are not to be considered as limitly tothe use of chromium oxide for the hydroing the scope thereof:

genation of sulphur compounds such as carbon E l I disulphide, alkylsulphides, thioaldehydes, mer- 8 captans and the like. The invention maybe used A solution of chromium nitrate is prepared by either for thepurpose of forming valuable interdissolving 2.0 lbs. of conmiercialchromium nimediate sulphur products, or for the purpose of trate inabout 2.0 liters of boiling water. This forming hydrogen sulphide andsaturated hydrois diluted to about 25 liters and chromium by- 10 carbonsas the end products of the hydrogenadroxide is precipitated from thesolution by add- 10 tion, ing a slight excess 01' ammonium hydroxide.The

It has not been practical in the past to catadark blue 'gelatinousprecipitate is broken up lytically hydrogenate sulphur compounds due toand'washed several times by decantation. After the poisoning eflect thatthese compounds have filtering, the material is dried at 110 C. A hard,

on the usual hydrogenation catalysts. Because black vitreous material isobtained which can 15 of this sensitivity of the best catalysts tosulphur be crushed to the desired size for immediate use poisoning, thewhole field of synthetic sulphur in hydrogenation.

compounds, which may possibly be obtained by I A cc. sample of thiscatalytic material size hydrogenation reactions analogous to the synto 8to 14 mesh was heated to about 480 C. in

20 thesis of methanol from carbon monoxide and an atmosphere ofhydrogen, and then a gaseous 20 hydrogen, has remained closed.Suggestions mixture containing 17% carbon disulphide and have been madeto the use of certain particular 83% hydrogen was passed over it at arate of catalysts for the hydrogenation of organic sulabout 8 to 10liters of gas per hour, while the" phur compounds in gases to hydrogensulphide. temperature was maintained at about 480 C. r

These catalysts that were suggested have all been The carbon disulphidewas almost completely 25 mixtures or chemical combinations containingconverted to methane and hydrogen sulphide. two or more components. Theymay include a Exam 16 H .metal of the sixth group of the periodic systemor its oxide or hydroxide with one or more metals A water-gas consistingof a mixture, of carbon oi the first to the fifth groups or theiroxidesor monoxide and hydrogen and containing undesir- 3o hydroxides. However,very little information has able traces of carbon disulphide andthiophene been given covering the details of preparing these was passedover a catalyst prepared as described catalysts with the result thatduplication of the in Example I at a temperature of about 480 C, work isnot possible. and at a space velocity of about 500 cc. of gas Thisinvention has as its object the catalytic per cc. oi catalyst per hour.The organic sul- 3.3 hydrogenation oi organic sulphur compounds phurcompounds were completely hydrogenated using a catalyst of onecomponent; namely, chroto hydrogen sulphide, which was readily removedmium oxide. A further object is the production by scrubbing the gas withwater. In place oi oi! synthetic organic sulphur compounds by hywaterfor the scrubbing step, inexpensive alkaline drogenation methodsanalogous to the synthesis reagents may be used. I

of methanol from water-gas. A still further ob- Example "I ject is thetreatment of substances such as gases, I

oils, and hydrocarbons, to remove-certain ob- A very active catalyst wasprepared by carejectionable sulphur compounds. Other objects fullyadding 200 to 250 cc. of concentrated sulof the invention will appearhereinafter. phuric acid to a solution of 150 cc. of methanol 45 Theseobjects are accomplished by bringing in 500 cc. of water. While hot, asolution of 150 the sulphur compound and hydrogen into cong. ammoniumbichromate in 500 cc. of water tact with chromium oxide. In the case ofthe was slowly added. The solution turned green, removal 01' certainobjectionable sulphur comindicating reduction of the hexavalentchromium,

pounds such as organic sulphides, mercaptans, and gaseous oxidationproducts of methanol were so and thiophene, from gases, oils andhydrocarevolved; The solution, which now contained av bons, thesecompounds may be destructively hychromium sulphate,was diluted withseveral voldrogenated to hydrogen sulphide which may be umes of water.Enough ammonium' hydroxide comparatively easily removed by washing, thuswas added to precipitate chromium hydroxide providing an inexpensivepurification process. as a blue-green insoluble powder, which was then55 washed several times by decantation, filtered and dried.

The experiment of Example II was repeated, using this substance as acatalyst and it was found that all the organic sulphur compounds werecompletely hydrogenated to hydrogen sulphide.

' Example IV A quantity of commercial benzene containing a small amountof thiophene as an impurity was vaporized and passed over 50 cc. of anamorphous chromium oxide catalyst prepared as described in Example I,together with hydrogen, at a temperature of 450 to 500 C. and at therate of about 200 cc. per hour. The thiophene was completely removed.

Example VI A solution containing approximately 200 g. of ammoniumbichromate per liter of water was treated with hydrogen sulphide untilno further precipitation occurred. The product was filtered and dried.The occluded sulphur-from the reaction was removed by heating thecatalyst in hydrogen. A mixture of ethylene, acetylene and hydrogensulphide was passed over the catalyst prepared in this manner, at atemperature of 350 to 500 C. The condensate contained liquid substancessuch as mercaptans, disulphides, thiophene, thioaldehydes, and otherproducts containing sulphur.

Example VII Ammonium bichromate is heated in a vacuum at 200 to 250 C.It slowly darkens and gradually evolves water, ammonia and nitrogen.After 4 to 5 hours there remains a glistening black residue whichcontains no ammonia and is slightly paramagnetic and stable up to 400 C.This proved to be a moderately active chromium oxide catalyst.

It should be understood that conditions other than those specified maybe effectively used, and variations of -the illustrated processes may becarried out in order to obtain certain desired effects. Carbondisulphide may be substituted for the hydrogen sulphide or added to thehydrogen sulphide content in Example VI, or the gas may be free ofacetylene. Such variations in the composition of the incoming gas variesthe composition of the valuable products obtained.

If lower temperatures are used in the carrying out of the process inExample I, various liquid products are formed as a result of the lessdrastic conditions.

The catalyst made in accordance with Example III is a light-blue chalkymaterial and may be used as such. or it may be briquetted and crushed tothe desired size before use.

Although we prefer to prepare the catalyst according to the directionsgiven, other variations than those already described may be made, withpractically equivalent results, and in some cases with advantages. Forinstance, the preparation of the catalyst in Example I is not confinedto the use of chromium nitrate and ammonium hydroxide, or even to theproportions and dilutions mentioned in that example. Chromium chloride.5 sulphate or chrome alum may be substituted for chromium nitrate, andother substances yielding an alkaline reaction, such as sodium orpotassium hydroxide, carbonate or sulphide may be used as theprecipitant.

Furthermore, the preparation of the catalyst strictly according toExample III, although preferred, is not necessary. For instance, othermineral acids may be used during reduction of the chromium. Otherprecipitants than ammonium hydroxide, and other reducing agents thanmethanol, such as formaldehyde, ethanol, acetone or hydrazine, hydrogensulphide, and many others may be used, often with advantage.

It is not necessary to confine the working range of the catalyst to thetemperatures mentioned in the examples. Other temperatures from 200 to800 C. may be used with corresponding varia tions in the nature of thereaction taking place. The preferred temperature range is between 300 to500 C. Variations may also be made in the ratio of hydrogen to thevarious substances be ing hydrogenated, although the hydrogen willpreferably be used in excess of the compound undergoing hydrogenation.

This invention has opened the entirely new field of synthesizing sulphurcompounds that may be obtained by the hydrogenation reactions analogousto the synthesis of methanol from carbon monoxide and hydrogen and,moreover, forms an inexpensive process for the removal of certainobjectionable sulphur compounds from gases. oils and hydrocarbons.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that we do not limit ourselves to the specific embodimentsthereof except as defined in the appended patent claims.

We claim:

1. A process of hydrogenating sulphur com pounds capable ofhydrogenation which comprises bringing a gaseous mixture containing asulphur compound capable of hydrogenation and an excess of hydrogen intocontact with a hydrogenation catalyst consisting of chromium oxide atsubstantially atmospheric pressure.

2. A process of hydrogenating sulphur compounds capable of hydrogenationwhich comprises bringing a gaseous mixture containing a sulphur compoundcapable of hydrogenation and an excess of hydrogen into contact with ahydrogenation catalyst consisting of chromium oxide at a temperature of200 to 800' C. and at substantially atmospheric pressure. 1

3. A process of hydrogenating sulphur compounds capable of hydrogenationwhich comprises bringing a gaseous mixture containing an organic sulphurcompound capable of hydrogenation and hydrogen into contact with ahydrogenation catalyst consisting of chromium oxide at a temperaturebetween 300 to 500 C. and at substantially atmospheric pressure.

4. The process of purifying hydrocarbons containing sulphur compoundscapable of hydrogention as an impurity, which comprises bringing agaseous mixture containing these hydrocarbons and hydrogen into contactwith a hydrogenation catalyst consisting of chromium oxide at atemperature of 300 to 500' C. and at substantially 7 atmosphericpressure, so as to convert the sulphur compound to hydrogen sulphide,and re;- moving the hydrogen sulphide.

5. In the process of removing sulphur compounds capable of hydrogenationfrom watergas, the step which comprises bringing the watergascontaminated with sulphur compounds capable oi hydrogenation intocontact with a hydrogenatlon catalyst consisting of chromium oxide at atemperature oi 350 to 500- C. and at substantially atmospheric pressure.

6. li'he process oi producing sulphur compounds capable of hydrogenationwhich comprises bringing a mixture of ethylene, acetylene, and hydrogensulphide into contact with chromium oxide at a temperature of 300 to 500C. and at substantially atmospheric pressure.

7. A process of hydrogenating sulphur compounds capable of hydrogenationwhich comprises bringing a gaseous mixture, consisting 01 carbonbisulphide and hydrogen, into contact witha hydrogenation catalystconsisting of chro-= mium oxide at a space velocity oi 400 to 500 cc.

of gases per cc. of catalyst per hour, and at substantially atmosphericpressure at a temperature of 480 C.

8. A process which comprises forming an aqueous chromium nitrate,solution, precipitating chromium hydroxide as a gelatinous precipitatefrom the solution by the addition of an alkali, separating-theprecipitate from the solution and drying same at about 100 C. to obtaina black vitreous material, bringing a gaseous mixture comprising asulphur compound and hydrogen 5 into contact with the black vitreousmaterial at a temperature between 300 to 500 C., and recovering thehydrogenated sulphur compounds formed.

9. A process which comprises dissolving two pounds of chromium nitratein 2 liters of boiling water, diluting the solution to 25 liters, addingammonium hydroxide in slight excess to precipitate chromium hydroxide asa dark blue gelatinous precipitate, breaking up the precipitate andwashing same by decantation, dryingthe washed precipitate at 100 C. toobtain a hard black vitreous chromium oxide catalyst, crushing saidcatalyst to a size oi about 8 to 14 mesh and bringing a gaseous mixtureconsisting of carbon bisulphide and hydrogen into contact with 20 cc. ofthe crushed catalyst while maintaining a temperature of about 480 C.,said gases being passed over the catalyst at a space velocity of about400 to 500 cc. of gas per cc. of catalyst per hour, recovering themethane and hydrogen sulphide formed.

WILBUR ARTHUR, LAZIER. JOHN VICTOR VAUGHEN.

